The propsed study is a clinical trial with long-term pharmacologically controlled hypertensive patients to test the effectiveness of potassium supplementation with and without dietary sodium reduction, in controlling blood pressure with reduced or no antihypertensive drugs. Using a randomized double-blind design, treated hypertensive patients who meet eligibility criteria will be assigned to one of three groups: Group 1 - dietary sodium reduction to less than or equal to 80 mEq/day plus placebo; Group 2 - dietary sodium reduction (less than or equal to mEq/day) and potassium supplementation, greater than or equal to 80 mEq/day in the form of wax matrix slow release potassium chloride tablets; and, Group 3 - maintenance on antihypertensive drugs. Groups 1 and 2 will consist of 150 individuals each, Group 3, 75 individuals, for a total study population of 375 hypertensives. After 12 weeks of intervention Groups 1 and 2 will be taken off antihypertensive medication and compared at subsequent "visits of record" as to being on or off antihypertensive medication. The two groups will also be compared in terms of those requiring antihypertensive medication for dose and number of medications needed to control blood pressure. The comparisons will be made at six month interval "visits of record" over two years of active intervention. Group 3 will provide a comparison group to account for spontaneous changes in medication regimens (due to toxic or side effects) and blood pressure. The study design incorporates careful blood pressure monitoring and strict comparative criteria for return to medication when indicated.